Rendering cooker

ABSTRACT

A material is rendered within a heated vessel or container which encloses a rotary agitator including a shaft driven by a hydraulic motor. Hydraulic fluid is supplied to the motor at a substantially constant pressure so that the motor transmits a substantially constant horsepower to the agitator shaft to effect an automatic increase in the rotational speed of the agitator when the required torque decreases and a decrease in speed when the torque increases.

United States Patent Bredeson Aug. 8, 1972 [54] RENDERING COOKER [72] Inventor: Dean K. Bredeson, Piqua, Ohio [73] Assignee: The French Oil Mill Machinery Company, Piqua, Ohio 22] Filed: March 16,1970

[21] App1.No.: 19,686

[52] US. Cl ..99/348, 23/2905 [51] Int. Cl. ..A47j 27/52 [58] Field of Search ..259/109, 110, 175, 176, 177, V 259/178; 99/234, 235, 348; 260/4126;

[56] References Cited UNITED STATES PATENTS 2,350,913 6/1944 Mercer ..318/11 3,272,599 9/ 1 966 Allbright ..260/412.6 2,650,807 9/1953 Bilek ..259/109 4/1959 Maxon ..259/177 A 3,062,515 1 1/ 1962 3,080,152 3/1963 3,371,543 3/1968 Jackson ..259/177 R 3,441,255 4/1969 lsta ..259/177 R Primary Examiner-Robert W. Jenkins Attorney-Marechal, Biebel, French & Bug

1 1 ABSTRACT A material is rendered within a heated vessel or container which encloses a rotary agitator including a shaft driven by a hydraulic motor. Hydraulic fluid is supplied to the motor at a substantially constant pressure so that the motor transmits a substantially constant horsepower to the agitator shaft toeffect an automatic increase in the rotational speed of the agitator when the required torque decreases and a decrease in speed when the torque increases.

6 Claim, 3 Drawing Figures RENDERING COOKER BACKGROUND OF THE INVENTION In the rendering of a material which changes consistency as it is being heated, as for example, in the rendering of poultry by-products such as offal and feathers, commonly the material is processed in batches within a horizontal cooker. The cooker consists of an elongated cylindrical vessel or container having an upper charging inlet and a bottom discharge outlet and defining a chamber adapted to receive a heating fluid such as. steam. An agitator is disposed within the container and includes an axially extending shaft which supports a plurality of paddle assemblies. The agitator shaft is rotatably supported at each end of the container and is connected at one end to a chain drive extending from a gear reducer driven by a constant speed electric motor;

During the rendering of a batch of material such as poultry by-products, the horsepower required to drive the agitator quickly increases as the cooker is charged with material. For example, in one installation, the power required increased to 50 horsepower when a batch was supplied to the cooker. Within approximately one-half hour, the load dropped to about 60 percent of the 50 horsepower or to approximately 30 horsepower. After a cooking period of about 2% hours, the load began to increase again to a level above the initial load or to about 60 horsepower as the by-products approach the glue or stick phase of the rendering process. During the next period of approximately one hour, the load dropped to approximately 60 percent of the initial feed load or about 30 horsepower until the batch of material is ready to be discharged.

The electric motor for driving the agitator is selected so that its maximum power output corresponded to the power required to drive the agitator during the glue phase of the cooking operation. Thus in the above example, a motor was selected to produce a maximum of 60 horsepower at a speed of 38 rpm which was held constant during the entire cooking process.

It has been determined that the time required for cooking the material can be significantly reduced by increasing the speed of the agitator which effectively increases the rate of evaporation of moisture from the material as it is being cooked and/or dehydrated. However, to rotate the agitator shaft at a higher constant speed and to provide the necessary torque during the glue" phase, requires the selection of a motor having a significantly higher horsepower and a substantially higher cost.

SUMMARY OF THE INVENTION The present invention is directed to the rendering of a material in a more efficient manner by automatically increasing the rotational speed of the agitator when the torque required to rotate the agitator decreases and decreasing the speed of the agitator when the torque increases. In accordance with one embodiment of the invention, this rendering technique is performed automatically within a rendering cooker having an agitator driven by a hydraulic motor. Hydraulic fluid is supplied to the motor from a pump which is driven by an electric motor, and the pressure of the hydraulic fluid is maintained substantially constant by a closed loop control system so that the horsepower transmitted from the hydraulic motor to the agitator shaft remains substantially constant. Thus when the torque required to drive the agitator shaft decreases during the cooking process as the viscosity of the material decreases, the rotational 'speed of the agitator increases to effect an increase in rendering the material' BRIEF DESCRIPTION OF THE DRAWING FIG. 1 shows a horizontal rendering cooker driven by a hydraulic drive system in accordance with the invention;

FIG. 2 is a vertical section taken generally on the line 2--2 of FIG. 1; and

FIG. 3 is a schematic of the hydraulic control system for the cooker drive shown in FIG. 1.

Referring to FIG. 1, a horizontal rendering cooker includes a cylindrical shell having dome-like end walls 11 and 12. A cylindrical inner wall 14 cooperates with the shell 10 to define a cylindrical or annular chamber 15. Hot fluid such as steam is supplied to the chamber 15 through one or more inlets l6 and is discharged from the chamber through bottom outlets 18. The shell 10 is supported by brackets 19 which mount on corresponding pedestals or bases 20.

The inner cylindrical wall 14 and the end walls 11 and 12 cooperate to define a cooking chamber which is adapted to receive a charge or batch of material to be rendered through an inlet duct 26 projecting upwardly from the shell 10. A cover 28 is pivotally connected to the duct 26 by a vertical pin 29 and is movable between an open position (FIG. 2) and a closed position (FIG. 1) where the cover is clamped and sealed to the inlet duct 26 by a latch 31 and a clamping screw 32. A vent pipe 35 is connected to the inlet duct 26 by a fitting 36 and is connected to a valve (not shown) for controlling a pressure build-up within the cooking chamber 25. The vent pipe 35 may also be connected to a suction pump to provide a partial vacuum in the chamber 25 if desired for rendering a particular material. A discharge outlet 38 is formed within the lower portion of the end wall 12 and receives a door 40 pivotable between an open position (not shown) and a closed position (FIG. 1) where a fluid tight seal is formed between the door and the end wall 12.

A rotary agitator or agitating assembly is disposed within the chamber 25 and includes a axially extending shaft 46 having a square cross-sectional configuration. A cylindrical shaft 48 extends from one end of the shaft 46 through a packing gland 49 and is rotatably supported by a bearing 51 mounted on a bracket 52 secured to the end wall 12 of the container. A cylindrical shaft 54 extends from the opposite end of the agitator shaft 46 through a corresponding packing gland 49 mounted on the end wall 11 and is rotatably supported by a bearing 56 mounted on a platform 58 secured to the end wall 11. A pair of side reinforcing plates 59 are secured to the edges of the platform 58'and also to the end wall 11 of the container to form a rigid cantilevered bracket.

A plurality of paddle assemblies are mounted on the square shaft 46 at axially spaced intervals, and each paddle assembly 65 includes a pair of diametrically opposed paddle arms 66 (FIG. 2) which are clamped to the shaft 46 by a set of bolts 67. A paddle plate 68 is secured to the outer end of each paddle arm 66 and is angled slightly relative to the axis of the shaft 46 to effect circulation of a material within the chamber 25 when the agitator is rotated. The paddle assembly 65 adjacent the end wall 12 also includes a wiper blade 69 which aids in discharging material through the outlet 38.

In accordance with the present invention, the shaft 54 of the agitator 45 is driven by a hydraulic motor 75 which is mounted on the outer end of the platform 58. The motor 75 has an output shaft 76 which is connected to the shaft 54 through a flexible coupling 78. One make of hydraulic motor which has provided satisfactory performance is Double A Staffa model B200 sold by Scott Equipment Company, Dayton,-

Ohio. This hydraulic motor is of the fixed displacement radial piston type having a maximum recommended speed of 175 rpm and a maximum continuous torque of 7350 foot pounds to produce a maximum horsepower rating of approximately 160 hp.

Hydraulic fluid is supplied to the motor 75 through a conduit or line 82 which is connected to a hydraulic pump 85 having an input shaft 86 connected to the output shaft of an electric motor 88 through a flexible coupling 89. One hydraulic pump which has been determined to be satisfactory for driving the hydraulic motor75 is a 24 series axial piston hydraulic pump with a constant horsepower control sold by Sunstrand. This pump is capable of producing a hydraulic pressure of 5000 psi and sufficient flow rate to drive the shaft 76 of the hydraulic motor 75 at a speed range of to 65 rpm. This hydraulic pump was driven by a 75 horsepower, 1800 rpm electric motor having a 1.15 service factor.

As shown in FIG. 1, the hydraulic pump 85 and the electric motor 88 are mounted on a reservoir tank 95 adapted to receive hydraulic fluid which is supplied to the hydraulic pump 85 through a supply line 96 having a filter 97. The fluid is returned to the tank 95 from the motor 75 through a return line 98 which extends through a heat exchanger 100. Referring to FIG. 3, the hydraulic pump 85 is capable of maintaining a substantially constant pressure within the supply line 82 so that the hydraulic motor 75 will transmit to the agitator shaft 54 a substantially constant horsepower. This is accomplished through a closed loop recirculating system including a fluid line 101 which connects the fluid supply line 82 to a pressure regulator 102 mounted on the hydraulic pump 85. The regulator is adjustable by a hand control knob 103 to change the pressure within the supply line 82, and a pressure gage 104 is connected to the line 101 to facilitate the selection of the fluid pressure within the line 82. If the hydraulic pressure within the supply line 82 begins to increase above a preselected value, as for example, 3100 psi, fluid is recirculated to the pump 85 through the line 101 and the pressure regulator 102.

As mentioned above, the fluid return line 98 from the hydraulic motor 75 to the reservoir tank 95 extends through a heat exchanger 100 so that the temperature of the hydraulic fluid does not exceed a predetermined upper limit during the operation of the cooker. The heat exchanger 100 is supplied with cooling water through a line 110 having a flow control valve 114 r which is regulated in response to a temperature sensing element 115 located within the reservoir tank 95. As the temperature of the hydraulic fluid increases, the valve 114 opens further to increase the flow rate of cooling water from the supply line 110 through the heat exchanger 100.

From the drawings and the above description, it is apparent that a rendering cooker having an agitator driven in accordance with the invention provides desirable features and advantages. For example, by driving the agitator shaft 54 with a motor which produces a substantially constant horsepower, the agitator 45 automatically increases in speed as the torque required to rotate the agitator decreases and decreases in speed when the required torque increases. As a result, when theconsistency or viscosity of the material being rendered decreases, and the torque required to drive the agitator decreases, the speed of the agitator automatically increases thereby increasing the rate of moisture removal or evaporation from the material as it is being cooked and/or dehydrated. This significantly reduces the overall time required for rendering a batch of material thereby enabling successive batches of material to be rendered more efficiently at a faster rate.

The hydraulic drive system for driving the agitator shaft 54 is especially desirable in that it provides an economical drive means for transmitting substantially constant horsepower to the drive shaft 54. For example, once the pressure of the hydraulic fluid in the supply line 82 is selected with the control knob 103, this pressure will remain substantially constant to the hydraulic motor causing the motor to produce a substantially constant horsepower output.

While the apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made in either without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. An improved cooker adapted for rendering a material which changes in consistency while being cooked, comprising a container, a rotatable agitator disposed within said container and having a shaft projecting therefrom, means for heating the material within said container, a hydraulic motor connected to said shaft of said agitator, and means including a regulated constant pressure fluid supply to said motor for automatically controlling said motor to effect a substantially constant horsepower transmission from said motor shaft to said agitator shaft for providing a more efficient cooking operation.

2. An improved cooker adapted for rendering a material which changes in consistency when it is heated, comprising a container, a rotatable agitator,

disposed within said container and having a shaft, means for heating the material within the container, a hydraulic motor having a shaft connected to said shaft of said agitator, a pump connected to supply hydraulic fluid to said motor, and means for controlling said motor to maintain a substantially constant pressure fluid supply to said motor to effect an automatic increase of the rotational speed of said agitator when the torque required to rotate said agitator decreases and an automatic decrease in the rotational speed of the agitator when the torque required to rotate said agitator increases for providing a more efficient cooking process.

3. A cooker as defined in claim 2 wherein said hydraulic motor has a shaft aligned with said shaft of said agitator, and coupling means connecting said shafts.

4. A cooker as defined in claim 2 wherein the controlling means includes an adjustable regulator for changing the pressure of the hydraulic fluid supplied to said motor from said pump to efiect a change in the horsepower transmitted to said agitator shaft.

5. A cooker as defined in claim 2 wherein said controlling means includes a fluid line connecting said fluid supply to said motor, pressure sensing means connected to said fluid line, and said pressure sensing means is effective when the pressure of said fluid supply increases above a preselected value to cause fluid to be recirculated from said fluid line to said pump" to maintain said substantially constant pressure.

6. A cooker as defined in claim 2 including a reservoir, a fluid return line connecting said motor to said reservoir, and means for cooling the fluid in said return line in response tothe temperature of the fluid in said reservoir. 

1. An improved cooker adapted for rendering a material which changes in consistency while being cooked, comprising a container, a rotatable agitator disposed within said container and having a shaft projecting therefrom, means for heating the material within said container, a hydraulic motor connected to said shaft of said agitator, and means including a regulated constant pressure fluid supply to said motor for automatically controlling said motor to effect a substantially constant horsepower transmission from said motor shaft to said agitator shaft for providing a more efficient cooking operation.
 2. An improved cooker adapted for rendering a material which changes in consistency when it is heated, comprising a container, a rotatable agitator disposed within said container and having a shaft, means for heating the material within the container, a hydraulic motor having a shaft connected to said shaft of said agitator, a pump connected to supply hydraulic fluid to said motor, and means for controlling said motor to maintain a substantially constant pressure fluid supply to said motor to effect an automatic increase of the rotational speed of said agitator when the torque required to rotate said agitator decreases and an automatic decrease in the rotational speed of the agitator when the torque required to rotate said agitator increases for providing a more efficient cooking process.
 3. A cooker as defined in claim 2 wherein said hydraulic motor has a shaft aligned with said shaft of said agitator, and coupling means connecting said shafts.
 4. A cooker as defined in claim 2 wherein the controlling means includes an adjustable regulator for changing the pressure of the hydraulic fluid supplied to said motor from said pump to effect a change in the horsepower transmitted to said agitator shaft.
 5. A cooker as defined in claim 2 wherein said controlling means includes a fluid line connecting said fluid supply to said motor, pressure sensing means connected to said fluid line, and said pressure sensing means is effective when the pressure of said fluid supply increases above a preselected value to cause fluid to be recirculated from said fluid line to said pump to maintain said substantially constant pressure.
 6. A cooker as defined in claim 2 including a reservoir, a fluid return line connecting said motor to said reservoir, and means for cooling the fluid in said return line in response to the temperature of the fluid in said reservoir. 